Apparatus for producing doubly curved concrete shells



May 12, 1964 w. J. SILBERKUHL ETAL 3,132,404

APPARATUS FOR PRODUCING DOUBLY CURVED CONCRETE SHELLS Filed Oct. 30, 1961 3 Sheets-Sheet 1 WILHELM IJOHANNES SILBERKUHL; UWE KASTL ERNST HAEUSSLE'R- BY {{INWORS.

AGENT y 12, 1964 w. J. SILBERKUHL ETAL 3,132,404

APPARATUS FOR PRODUCING DOUBLY CURVED CONCRETE SHELLS Filed Oct. 30, 1961 3 Sheets-Sheet 2 IFIG.2

Q WILHELM JOHANNES SILBERKUHL N UWE KASTL ERNST HAEUSSLER INVENTORS.

AGENT May 12, 1954 w. .1. SILBERKUHL ETAL 3,132,404

- APPARATUS FOR PRODUCING DOUBLY CURVED CONCRETE. SHELLS Filed Oct. 50, 1961 s Sheets-Sheet 5 FIG-,3

WILHELM JOHANNES SILBERKUHL UWE KASTL ERNST HAEUSSLER I VENTORS. BY W? M AGENT United States Patent 3,132,404 APPARATUS FOR PRODUCING DOUBLY CURVED CONCRETE SHELLS Wilhelm Johannes Silberkuhl, Uwe Kastl, and Ernst Haeussler, all of Moorenstr. 24, Essen, Germany Filed Oct. 30, 1961, Ser. No. 148,762 7 Claims. (Cl. 25-418) Our present invention relates to an apparatus for producing poured concrete shells that are curved in mutually orthogonal planes, e.g., for the purpose of making a prestressed roof structure with a vault of generally hyperboloidal curvature as disclosed in copending application Ser. No. 715,750, filed February 17, 1958, by Wilhelm I. Silberkuhl, now abandoned.

The general object of our invention is to provide means for facilitating the manufacture of shells of this type.

It is desirable to smooth the upper surface of such shell, poured in a suitable mold, with the aid of a vibratory slider of arcuate configuration which contacts this surface along a relatively narrow transverse zone and whose curvature corresponds to the transverse curvature of the shell, the slider traveling in longitudinal direction of the poured slab along rails curved in conformity with the longitudinal shell curvature.

We have found, however, that this measure alone does not always satisfy the exacting requirements of modern building construction since the concrete, which still retains some degree of fluidity when contacted by the smoothing device, tends to surge up behind the slider and to change the cross-section of the shell accordingly. Thus, a more particular object of our invention is to provide a device of this character which avoids this drawback.

In accordance with this invention we provide a smoothing device including a rail-borne carriage from which the vibratile slider is suspended, preferably in a forward direction, along with a weighted-down trailer of similar bottom curvature, the two curved members being so attached to each other and/ or the carriage that only a flexible connection exists therebetween so that the vibrations of the slider are not communicated to the trailer.

More particularly, we prefer to provide resilient suspension means between the carriage and the slider while rigidly connecting the trailer with the carriage; a flexible strip spanning the width of the concrete slab may bridge the gap between the slider and the trailer. The extent of the trailer in the direction of travel is so chosen in relation to carriage speed that the concrete has substantially set at the location where the rear edge of the trailer is in contact with its surface.

The invention will be described in greater detail with reference to the accompanying drawing in which:

FIG. 1 is a top-plan view of part of a shell mold in combination with a smoothing device embodying our invention;

FIG. 2 is a cross-sectional view of the mold taken on the line II-II of FIG. 1 and showing the smoothing device in elevation; and

FIG. 3 is a sectional view of the device taken on the line III-III of FIG. 2.

As illustrated in the drawing, a mold 20 forms a cavity 21 for a concrete shell 22 in which prestressing cables 23 and other reinforcements, not shown, are imbedded in a manner known per se. Rails 3 extend along the lateral walls of the mold 20 and are bent, as seen in FIG. 3, in accordance with the longitudinal curvatures of the mold cavity. A carriage 24, comprising a horizontal frame 6 supported on rollers 5, rides above the cavity 21 on rails 3 and is propelled therealong by suitable means such as a pair of tow ropes 25 engaging lugs 26 in a depending shield 7 which is rigid with frame 6.

A set of brackets 8, bolted to the forward side of shield 7, are fastened through rubber bumpers 4 to an arcuate slide member 1 comprising two arcuate sheet-metal bars 1a, 1b of inversely L-shaped profile; the curvatures of these bars conform to the transverse curvature of mold cavity 21 seen in FIG. 2, the underside of bar 1a skimming the top of the cavity to smoothen the concrete layer 22 as the carriage 24 advances along the rails 3. A vibrator motor 27 is fastened to the horizontal underside of bar 1b, within the space encompassed by the two bars, and drives an eccentrically pivoted arm 28 which is hinged to bar 1a whereby the slider 1 is resiliently deformed and oscillates relatively to plate 7 and carriage 24. Bar Ia also carries forwardly extending fins 29 designed to help communicate the vibrations of the slider to the concrete surface.

A box-shaped trailer 2, weighted down by a load of gravel 30, is rigidly bolted to the rear face of plate 7 so that its underside, conforming to the curvature of slider 1, bears upon the surface of shell 22 almost as soon as the slider has passed over it. The cantilevered trailer 2 is insulated against the vibrations of slider 1 by being connected with it only through the resilient bumpers 4 and a rubber strip 9 which is fastened by screws 31 to projecting ledges 10, 11 of the carriageentrained members 1, 2. Strip 9, which spans the gap between these members over the full width of cavity 21, prevents the intrusion of concrete into that gap.

It will thus be apparent that the trailer 2, which is shown substantially coextensive in its lower profile with slider 1 but overlies a wider portion of the concrete slab than does the slider, imparts a smooth finish to the slab while maintaining the curvature given to it by the vibratory member. The rate of advance of carriage 24 along the rails 3 is so chosen that the concrete will have substantially hardened at the instant when it is uncovered by the rear edge of the trailer.

We claim:

1. Apparatus for producing doubly curved concrete shells, comprising a mold conforming to the shape of a shell to be poured and having curvature in two orthogonal dimensions, rail means extending along said mold, said rail means having a curvature equaling that of the upper shell surface in one dimension, a carriage displaceable along said rail means, a vibratile slider member mounted on said carriage and extending across the top of the mold cavity in a direction transverse to said rail means with a bottom curvature equaling that of the upper shell surface in another dimension orthogonal to said one dimension, a trailer member connected with said carriage while extending acrossthe top of the mold cavity behind said slider member with a bottom curvature equaling that of the latter, fastening means securing said members to said carriage for entrainment thereby in said one dimension while insulating said trailer member against the vibrations of said slider member, said members being secured to said carriage with mutual separation in said one dimension, and flexible link means bridging the gap between said members just above the top of said mold cavity and extending completely across said cavity for preventing the intrusion of concrete into said gap.

2. Apparatus according to claim 1 wherein said fastening means comprises resilient suspension means joining said slider member to said carriage, said trailer member being rigid with said carriage.

3. Apparatus according to claim 2 wherein said resilient suspension means comprises a set of elastic bumpers.

4. Apparatus according to claim 1 wherein said flexible link means comprises an elastic strip.

5. Apparatus according to claim 1 wherein said trailer member extends along said upper shell surface in said one dimension over a greater distance than does said slider member.

6. Apparatus according to claim 1 wherein said trailer member is provided with weighting means for maintaining it in contact with said upper shell surface.

7. Apparatus according to claim 6 wherein said trailer member is in the shape of a box with curved bottom, said weighting means comprising a filler material in said box.

References Cited in the file of this patent UNITED STATES PATENTS 10 2,032,736 Briggs Mar. 3, 1936 2,094,974 Wood Oct. 5, 1937 2,306,125 Jackson Dec. 22, 1942 2,346,378 Jackson Apr. 11, 1944 OTHER REFERENCES Construction Methods article, Shaped Earth Is Casting Bed for Roof Arches, December 1960, pages 56-58. 

1. APPARATUS FOR PRODUCING DOUBLY CURVED CONCRETE SHELLS, COMPRISING A MOLD CONFORMING TO THE SHAPE OF A SHELL TO BE POURED AND HAVING CURVATURE IN TWO ORTHOGONAL DIMENSIONS, RAIL MEANS EXTENDING ALONG SAID MOLD, SAID RAIL MEANS HAVING A CURVATURE EQUALING THAT OF THE UPPER SHELL SURFACE IN ONE DIMENSION, A CARRIAGE DISPLACEABLE ALONG SAID RAIL MEANS, A VIBRATILE SLIDER MEMBER MOUNTED ON SAID CARRIAGE AND EXTENDING ACROSS THE TOP OF THE MOLD CAVITY IN A DIRECTION TRANSVERSE TO SAID RAIL MEANS WITH A BOTTOM CURVATURE EQUALING THAT OF THE UPPER SHELL SURFACE IN ANOTHER DIMENSION ORTHOGONAL TO SAID ONE DIMENSION, A TRAILER MEMBER CONNECTED WITH SAID CARRIAGE WHILE EXTENDING ACROSS THE TOP OF THE MOLD CAVITY BEHIND SAID SLIDER MEMBER WITH A BOTTOM CURVATURE EQUALING THAT OF THE LATTER, FASTENING MEANS SECURING SAID MEMBERS TO SAID 